Warning:
Take care with transmitter circuits. It is illegal in most countries to operate radio
transmitters without a license. Although only low power this circuit may be tuned to operate over the range
87-108MHz with a range of 20 or 30 metres.

Notes
I have used a pair of BC548 transistors
in this circuit. Although not strictly RF transistors, they still give
good results. I have used an ECM Mic insert from Maplin Electronics, order
code FS43W. It is a two terminal ECM, but ordinary dynamic mic inserts can also
be used, simply omit the front 10k resistor. The coil L1 was again from Maplin,
part no. UF68Y and consists of 7 turns on a quarter inch plastic former with a tuning slug. The tuning slug is
adjusted to tune the transmitter. Actual range on my prototype tuned from 70MHz to around 120MHz. The aerial
is a few inches of wire. Lengths of wire greater than 2 feet may damp oscillations and not allow the circuit
to work. Although RF circuits are best constructed on a PCB, you can get away with veroboard, keep all leads
short, and break tracks at appropriate points.

One final point, don't hold the circuit
in your hand and try to speak. Body capacitance is equivalent to a 200pF capacitor shunted to earth, damping
all oscillations. I have had some first hand experience of this problem. The frequency of oscillation
can be found from the theory section,and an example now appears in
the Circuit Analysis section.